System and method for power supply noise reduction

ABSTRACT

An electrosurgical system includes an electrosurgical generator, a power source configured to deliver power to at least one load connected to the generator, a master configured to generate an initial pulse, the initial pulse cooperating with a first floating power supply configured to create an electrical connection between at least one first load and the power source, and a plurality of slaves connected in series to the master, wherein a first slave is configured to generate a subsequent pulse based on the initial pulse, the subsequent pulse cooperating with a second floating power supply configured to create an electrical connection between at least one second load and the power source, the subsequent pulse configured to cause an ensuing slave to generate an additional pulse, the additional pulse cooperating with a corresponding floating power supply configured to create an electrical connection between at least one additional load and the power source.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority as a divisional application to U.S.patent application Ser. No. 12/556,770, filed Sep. 10, 2009, thecontents of which are incorporated herein by reference.

BACKGROUND

1. Technical Field

The present disclosure relates to an electrosurgical system and methodand, more particularly, to pulse sequencing to minimize current draw ona shared power supply.

2. Background of Related Art

Energy-based tissue treatment is well known in the art. Various types ofenergy (e.g., electrical, ohmic, resistive, ultrasonic, microwave,cryogenic, laser, etc.) are applied to tissue to achieve a desiredresult. Electrosurgery involves application of high radio frequencyelectrical current to a surgical site to cut, ablate, coagulate or sealtissue. In monopolar electrosurgery, a source or active electrodedelivers radio frequency energy from the electrosurgical generator tothe tissue and a return electrode carries the current back to thegenerator. In bipolar electrosurgery, one of the electrodes of thehand-held instrument functions as the active electrode and the other asthe return electrode. The return electrode is placed in close proximityto the active electrode such that an electrical circuit is formedbetween the two electrodes (e.g., electrosurgical forceps). In thismanner, the applied electrical current is limited to the body tissuepositioned between the electrodes.

Typically, multiple isolated power supplies are connected to the activeterminals of the electrosurgical generator to power analog circuitsassociated with components connected to the electrosurgical generator(e.g., bipolar instruments, monopolar instruments, footswitches, etc.).For example, analog circuits configured to detect connected componentsand/or switching thereof may be included within the generator or withinthe connected components. Often, these isolated power supplies share thesame low voltage power source. This is problematic when multiplesupplies draw power from the shared power source substantiallysimultaneously, thereby maximizing the peak current draw on the sharedpower source. For example, the combined primary currents generated bycertain isolated power supplies activated substantially simultaneouslymay be large enough to cause a decrease in output of the shared powersource due to its output impedance or internal resistance. This decreasein output may cause output noise on the analog circuits drawing powertherefrom, if those analog circuits do not have adequate power supplyrejection bandwidth at the switching frequency of the isolated powersupply to which they are connected.

SUMMARY

According to an embodiment of the present disclosure, a method forminimizing current draw on a power source for an electrosurgical systemincludes the step of generating a first pulse signal from a masterdevice to electrically cooperate with a first floating power supplyconfigured to create an electrical connection between one or more firstloads and a power supply. The method also includes the step oftriggering an ensuing pulse signal from a slave device based on thefirst pulse signal to electrically cooperate with a subsequent floatingpower supply configured to create an electrical connection between oneor more subsequent loads and the power supply.

According to another embodiment of the present disclosure, a method forminimizing current draw on a power source for an electrosurgical systemincludes the steps of generating a first pulse signal and activating afirst floating power supply based on the first pulse signal. The firstfloating power supply is configured to deliver power from a power sourceto one or more first loads. The method also includes the steps ofgenerating a second pulse signal based on the first pulse signal andactivating a second floating power supply based on the second pulsesignal. The second floating power supply is configured to deliver powerfrom the power source to one or more second loads. The method alsoincludes the steps of generating an ensuing pulse signal based on apreviously generated pulse signal and activating a subsequent floatingpower supply based on the ensuing pulse signal. The subsequent floatingpower supply is configured to deliver power from the power source to oneor more additional loads.

According to another embodiment of the present disclosure, anelectrosurgical system includes an electrosurgical generator adapted tosupply electrosurgical energy to tissue and a power source operablycoupled to the electrosurgical generator and configured to deliver powerto one or more loads connected to the electrosurgical generator. Thesystem also includes a master device configured to generate an initialpulse signal. The initial pulse signal electrically cooperates with afirst floating power supply configured to create an electricalconnection between one or more first loads and the power source. Aplurality of slave devices are connected in series to the master device.A first slave device is configured to generate a subsequent pulse signalbased on the initial pulse signal. The subsequent pulse signalelectrically cooperates with a second floating power supply configuredto create an electrical connection between one or more second loads andthe power source. The subsequent pulse signal is configured to cause anensuing slave device to generate an additional pulse signal. Theadditional pulse signal electrically cooperates with a correspondingfloating power supply configured to create an electrical connectionbetween at least one additional load and the power source.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the present disclosure are described herein withreference to the drawings wherein:

FIG. 1A is a schematic block diagram of a monopolar electrosurgicalsystem in accordance with an embodiment of the present disclosure;

FIG. 1B is a schematic block diagram of a bipolar electrosurgical systemin accordance with an embodiment of the present disclosure;

FIG. 2 is a schematic block diagram of a generator in accordance with anembodiment of the present disclosure;

FIG. 3 is a schematic block diagram of specific components of thegenerator of FIG. 2 in accordance with an embodiment of the presentdisclosure; and

FIG. 4 is a circuit diagram of a power supply according to an embodimentof the present disclosure.

DETAILED DESCRIPTION

Particular embodiments of the present disclosure are describedhereinbelow with reference to the accompanying drawings. In thefollowing description, well-known functions or constructions are notdescribed in detail to avoid obscuring the present disclosure inunnecessary detail.

The generator according to the present disclosure can perform monopolarand bipolar electrosurgical procedures, including vessel sealingprocedures. The generator may include a plurality of outputs forinterfacing with various electrosurgical instruments (e.g., a monopolaractive electrode, return electrode, bipolar electrosurgical forceps,footswitch, etc.). Further, the generator includes electronic circuitryconfigured for generating radio frequency power specifically suited forvarious electrosurgical modes (e.g., cutting, blending, division, etc.)and procedures (e.g., monopolar, bipolar, vessel sealing).

FIG. 1A is a schematic illustration of a monopolar electrosurgicalsystem according to one embodiment of the present disclosure. The systemincludes an electrosurgical instrument 2 (e.g., monopolar) having one ormore electrodes for treating tissue of a patient P (e.g.,electrosurgical cutting, ablation, etc.). More particularly,electrosurgical RF energy is supplied to the instrument 2 by a generator20 via a supply line 4, which is connected to any one of a plurality ofactive terminals 30 a, 30 b, 30 c, . . . 30 m (see FIG. 2) of thegenerator 20, allowing the instrument 2 to coagulate, seal, ablateand/or otherwise treat tissue. The energy is returned to the generator20 through a return electrode 6 via a return line 8 at a return terminal32 (see FIG. 2) of the generator 20. The active terminals 30 a, 30 b, 30c, . . . 30 m and the return terminal 32 are connectors configured tointerface with plugs (not explicitly shown) of the instrument 2 and thereturn electrode 6, which are disposed at the ends of the supply line 4and the return line 8, respectively.

FIG. 1B is a schematic illustration of a bipolar electrosurgical systemaccording to the present disclosure. The system includes a bipolarelectrosurgical forceps 10 having one or more electrodes for treatingtissue of a patient P. The electrosurgical forceps 10 includes opposingjaw members 11 and 13 having an active electrode 14 and a returnelectrode 16, respectively, disposed therein. The active electrode 14and the return electrode 16 are connected to the generator 20 throughcable 18, which includes the supply and return lines 4, 8 coupled to theactive terminals 30 a, 30 b, 30 c, . . . 30 m and return terminal 32,respectively (see FIG. 2). The electrosurgical forceps 10 is coupled tothe generator 20 at a connector 21 having connections to the activeterminals 30 a, 30 b, 30 c, . . . 30 m and return terminal 32 (e.g.,pins) via a plug disposed at the end of the cable 18, wherein the plugincludes contacts from the supply and return lines 4, 8.

The generator 20 includes suitable input controls (e.g., buttons,activators, switches, touch screen, etc.) for controlling the generator20. In addition, the generator 20 may include one or more displayscreens for providing the user with variety of output information (e.g.,intensity settings, treatment complete indicators, etc.). The controlsallow the user to adjust power of the RF energy, waveform parameters(e.g., crest factor, duty cycle, etc.), and other parameters to achievethe desired waveform suitable for a particular task (e.g., coagulating,tissue sealing, intensity setting, etc.).

FIG. 2 shows a schematic block diagram of the generator 20 having acontroller 24, a DC power supply 27, and an RF output stage 28. Thepower supply 27 is connected to a conventional AC source (e.g.,electrical wall outlet) and includes a low voltage power supply 29(“LVPS”) and a high voltage power supply (not explicitly shown). Thehigh voltage power supply provides high voltage DC power to an RF outputstage 28, which then converts high voltage DC power into RF energy. RFoutput stage 28 delivers the RF energy to the plurality of activeterminals 30 a, 30 b, 30 c, . . . 30 m separately through a single-inputmultiple output multiplexer 35. The energy is returned thereto via thereturn terminal 32. The LVPS 29 provides power to various components ofthe generator (e.g., input controls, displays, etc.), as will bediscussed in further detail below.

The generator 20 may include a plurality of connectors to accommodatevarious types of electrosurgical instruments (e.g., instrument 2,electrosurgical forceps 10, etc.). Further, the generator 20 may beconfigured to operate in a variety of modes such as ablation, monopolarand bipolar cutting coagulation, etc. The generator 20 may also includea switching mechanism (e.g., relays) to switch the supply of RF energybetween the connectors, such that, for example, when the instrument 2 isconnected to the generator 20, only the monopolar plug receives RFenergy.

The controller 24 includes a microprocessor 25 operably connected to amemory 26, which may be volatile type memory (e.g., RAM) and/ornon-volatile type memory (e.g., flash media, disk media, etc.). Themicroprocessor 25 includes an output port that is operably connected tothe power supply 27 and/or RF output stage 28 allowing themicroprocessor 25 to control the output of the generator 20 according toeither open and/or closed control loop schemes. Those skilled in the artwill appreciate that the microprocessor 25 may be substituted by anylogic processor (e.g., control circuit) adapted to perform thecalculations discussed herein.

A noise reduction circuit 40 is operably coupled to the controller 24and is configured to control power drawn on the LVPS 29 by one or moreisolated floating power supplies 50, 52, 54, . . . “m”. Each supply 50,52, 54 . . . “m” may be an isolated power converter such as, forexample, a so-called “flyback converter” electrically connected to theLVPS 29 and configured to power a load 51, 53, 55, . . . “x”,respectively (see FIG. 3). Load 51, 53, 55, . . . “x” may be, forexample, one or more low-signal-level analog circuits configured todetect switching of a handset (e.g., instrument 2, forceps 10, etc.)connected to one of the plurality of connectors of generator 20 and/ordrawing energy from RF output stage 28 via any one of active terminals30 a, 30 b, 30 e, . . . 30 m. As shown in the illustrated embodiment ofFIG. 2, supplies 50, 52, 54, . . . “in” float at corresponding activeterminals 30 a, 30 b, 30 c, . . . 30 m and share the same low voltagepower source (e.g., LVPS 29). This is problematic when multiple suppliesdraw power from LVPS 29 substantially simultaneously, thereby maximizingthe peak current draw from LVPS 29. In the scenario wherein supplies 50,52, 54, . . . “m” are embodied as flyback converters, for example, thecombined primary currents generated by flyback converters activatedsubstantially simultaneously may be large enough to cause a drop inoutput of LVPS 29 due to the output impedance or internal resistance ofLVPS 29. This drop in output of LVPS 29 may cause output noise oncircuits (e.g., load 51, 53, 55, . . . “x”) drawing power therefromespecially if those circuits do not have adequate power supply rejectionbandwidth at the switching frequency of the power supply (e.g., supplies50, 52, 54, . . . “m”).

FIG. 3 shows a circuit schematic of the noise reduction circuit 40.Noise reduction circuit 40 includes a master device 42 and one or moreslave devices 44, 46, . . . “n” connected in series therewith. Masterdevice 42 and each of slave devices 44, 46, . . . “n” may be anintegrated circuit such as, for example, a 555 timer having an RCnetwork (not shown). In a so-called “monostable mode,” 555 timers act asa “one-shot” pulse generator. The one-shot pulse initiates when the 555timer receives a trigger signal (e.g., a one-shot pulse from a previous555 timer). Upon receiving the trigger signal, the 555 timer outputs theone-shot pulse as a function of a time constant of the RC network. In ascenario wherein a 555 timer is sequenced or chained to ensuing 555timers, this configuration has the effect of each ensuing 555 timerreceiving, as input, a one-shot pulse generated by the previous 555timer to trigger a one-shot pulse output as a function of the timeconstant. That is, for a given 555 timer, a time delay exists betweenthe reception of a trigger pulse and an output pulse as dictated by thetime constant of the RC network of that 555 timer. In this manner, theone-shot pulses generated by a chain of 555 timers are sequenced orchained in accordance with the time constant of the RC network for each555 timer, thereby minimizing the peak current draw on the common powersource (e.g., LVPS 29) to which they are connected.

With this scenario in mind, master device 42 is configured to generate apulse signal (e.g., a master switching frequency) that operates to causea load 51 connected to supply 50 to draw power from LVPS 29. The pulsesignal generated by master device 42 triggers slave device 44 tosubsequently generate a one-shot pulse, as discussed above with respectto monostable mode of operation for a 555 timer, that operates to causea load 53 connected to supply 52, to draw power from LVPS 29. Further,the one-shot pulse generated by slave device 44 triggers ensuing slavedevice 46 to generate a one-shot pulse that operates to cause a load 55connected to supply 54 to draw power from LVPS 29. Further, the one-shotpulse generated by slave device 46 triggers an ensuing slave device “n”to operate in like manner to the previous slave devices 44 and 46. Thatis, each ensuing slave device “n” connected in series with master device42 is configured to receive a triggering one-shot pulse from a previousslave device “n−1” and, in turn, subsequently generate a one-shot pulseto cause a load “x” connected to an ensuing supply “in” to draw powerfrom LVPS 29. In this manner, a sequenced or chained activation ofsupplies 50, 52, 54, . . . “n” (as opposed to substantially simultaneousactivation thereof), minimizes the peak current draw on LVPS 29. This,in turn, minimizes output noise on loads 51, 53, 55, . . . “x” connectedto supplies 50, 52, 54, . . . “n”, respectively, as discussedhereinabove.

In other embodiments, each of slave devices 44, 46, . . . “n” may be aso-called “tapped delay line” configured to simulate an echo of a sourcesignal generated by master device 42 to sequentially activate supplies50, 52, 54, . . . “n”.

By way of example, FIG. 4 illustrates a circuit diagram of a flybackconverter 70 including a transformer 60 having a primary winding 61 aand a secondary winding 61 b. Primary winding 61 a is connected inseries with a switching component 68 (e.g., a transistor). Secondarywinding 61 b is connected in series with a diode 62, both of which arein parallel with a capacitor 64 and a load 66 (e.g., analog circuit). Inoperation, a pulse signal generated by master device 42, or any one ofensuing slave devices 42, 44, 46, . . . “n”, closes or turns onswitching component 68. When switching component 68 is on or closed, theprimary coil 61 a of inductor 60 is directly connected to the LVPS 29,resulting in an increase of magnetic flux in the transformer 60 and apositive voltage across the secondary winding 61 b of transformer 60.This positive voltage across the secondary winding 61 b causes diode 62to be forward-biased and, as a result, the energy stored in transformer60 is transferred to the capacitor 64 and/or the load 66. When theswitching component 68 is off or open, as shown in FIG. 4, thetransformer GO induces a negative voltage across secondary winding 61 bsufficient to cause diode 62 to be reverse-biased (or blocked) and, as aresult, the capacitor 64 supplies energy to the load 66.

While several embodiments of the disclosure have been shown in thedrawings and/or discussed herein, it is not intended that the disclosurebe limited thereto, as it is intended that the disclosure be as broad inscope as the art will allow and that the specification be read likewise.Therefore, the above description should not be construed as limiting,but merely as exemplifications of particular embodiments. Those skilledin the art will envision other modifications within the scope and spiritof the claims appended hereto.

What is claimed is:
 1. An electrosurgical system, comprising: anelectrosurgical generator adapted to supply electrosurgical energy totissue; a power source operably coupled to the electrosurgical generatorand configured to deliver power to at least one load connected to theelectrosurgical generator; a master device configured to generate aninitial pulse signal, the initial pulse signal electrically cooperatingwith a first floating power supply configured to create an electricalconnection between at least one first load and the power source; and aplurality of slave devices connected in series to the master device,wherein a first slave device is configured to generate a subsequentpulse signal based on the initial pulse signal, the subsequent pulsesignal electrically cooperating with a second floating power supplyconfigured to create an electrical connection between at least onesecond load and the power source, the subsequent pulse signal configuredto cause an ensuing slave device to generate an additional pulse signal,the additional pulse signal electrically cooperating with acorresponding floating power supply configured to create an electricalconnection between at least one additional load and the power source. 2.The electrosurgical system according to claim 1, wherein at least one ofthe master device and the plurality of slave devices is a 555 timerconfigured to generate a one-shot pulse signal.
 3. The electrosurgicalsystem according to claim 1, wherein at least one of the floating powersupplies is a flyback converter.
 4. The electrosurgical system accordingto claim 1, wherein the power source is a low voltage power supply. 5.The electrosurgical system according to claim 1, wherein at least one ofthe initial pulse signal, subsequent pulse signal, or additional pulsesignal is a one-shot signal.
 6. The electrosurgical system according toclaim 1, wherein the system is configured to sequence the initial pulsesignal and the subsequent pulse signal, such that the electricalconnection between the at least one first load and the power source iscreated substantially prior to the electrical connection between thesecond or additional load and the power source.
 7. The electrosurgicalsystem according to claim 1, wherein the system is configured togenerate a time delay between each pulse, such that the electricalconnection between the at least one first load and the power source iscreated substantially prior to the electrical connection between thesecond or additional load and the power source.
 8. The electrosurgicalsystem according to claim 7, wherein the time delay is a function of atime constant of an RC network.
 9. The electrosurgical system accordingto claim 1, further comprising a 555 timer configured to generate atleast one of the initial pulse signal and the subsequent pulse signal.